1. Field of the Invention
This invention relates to the field of smoke hoods for removing grease and smoke from the spaces above cooking appliances, particularly in restaurants.
2. Description of Prior Art
The original patent in the field of vortex-type smoke hoods for cooking appliances is U.S. Pat. No. 3,664,255, issued May 23, 1972. Although the invention of such patent is believed to be a major one, the specific apparatus shown and described therein did not permit achievement of the fullest benefits of the large upper vortex. Stated more specifically, the velocity of the supply air in the apparatus of such patent could be increased only to a limited extent. Further increases resulted in "bouncing" or "rebounding" of supply air and of entrained fumes down out of the hood and into the room.
A relatively high velocity of supply air to the vortex, especially the upper vortex, is important for a number of reasons. The vortex principle causes a first centrifugal separation of grease to occur in the capture chamber, before the air and fumes pass through the filter. An analogy to the centrifugal grease separation in the upper vortex would be a jet traveling at high speed toward a cliff to bomb a target on the side thereof. As the jet (analogous to the air) pulls up, the bomb (analogous to a grease particle) is released -- so that the forward "bomb" (grease) velocity sends it at high speed into the cliff (analogous to the filter). The grease after impinging against the filter clings thereto instead of passing up the chimney. A second centrifugal grease separation action then occurs in the filter itself, as stated below.
The faster the air flow in the vortex (especially the upper vortex) in the capture chamber, the more effective the stated centrifugal grease-separation action therein.
Additional important reasons for creating a high-velocity upper vortex include a substantial simplification in the method by which the apparatus is set up for use. As explained in the above-cited patent, by far the greatest part of the air which passes out through the filters is not supplied from the room (the kitchen) but instead comes directly from the outside of the room. For example, in a typical installation only about 10% of the air comes from the room whereas 90% of the air comes from the outside. In attempting to achieve the desired balance between air supply to the hood, and air exhaust therefrom, it is important that the operator not be hampered by inability to increase the volume of the air supply sufficiently by increasing its velocity. As stated above, the operator would be so hampered if the otherwise-desired intake air velocity were so great as to cause rebound of air and smoke into the room.
The present apparatus achieves very effective separation of grease from the cooking fumes, yet permits a relatively simple set-up procedure. Furthermore, it is capable of withstanding substantial variations in the speeds of the supply and exhaust blowers (that is, speeds of the supply and exhaust air) without malfunctioning to a substantial degree.
Relative to a different aspect of the present disclosure, there have long existed restaurants which have plate shelves and/or pass-throughs beneath the smoke hoods. However, such restaurants did not achieve anything approximating the economy, efficiency, etc., of the shelf-smoke hood combination disclosed herein. In particular, there were no (insofar as applicant is aware) forced-flow smoke hoods which were so constructed that only a natural convective flow of air and cooking fumes passed upwardly adjacent the pass-through and/or the plate shelf.
In the above-cited patent, the baffle plate or member 54 was adjustable as described therein. The baffle 18 of the present disclosure is preferably (for economy reasons) fixed instead of adjustable. Such fixed baffle 18, the lip 19 at the rear edge thereof, and the central support 22 therefor, have all been on the market more than one year prior to the filing date of the present application and thus constitute prior art.